#include <iostream>

int main() {
    int max();
    extern int A, B, C;
    printf("Please enter three integer numbers: ");
    scanf("%d %d %d", &A, &B, &C);
    printf("max is %d", max());
    return 0;
}

int A, B, C;

int max() {
    int m;
    m = A > B ? A : B;
    return (C > m ? C : m);
}
